Thanks for the reply Dave. It seems that jena.apache.org/documentation/ontology/index.html Fig. 5 explains what you are explaining in your email. I still believe thought that javadocs should be more clear about this.
Thanks again Regards Papadakos Panagiotis On Tue, Jan 29, 2013 at 3:24 PM, Dave Reynolds <dave.e.reyno...@gmail.com>wrote: > On 24/01/13 13:08, Panagiotis Papadakos wrote: > >> Ian and Dave, thank you both for your help. >> >> I didn't post the correct code and I am sorry for this. >> >> Regarding the ontology, I know it is not correct. >> Maybe changing Europe to European, Germany to German, etc. would be >> better. >> >> Now regarding the listInstances method, I still believe something is >> wrong either in the code, in the API or in my way of thinking. >> >> listInstances is supposed to return the instances, either direct or >> instances of its subclasses. Unfortunately if I use a simple RDF_MEM >> model with no inference, listInstances(false) for the Manufacturer class >> returns no result. Somehow I feel this is wrong. >> I was thinking that internally, since there is no inference, jena should >> visit each subclass, and the subclasses of them, etc. getting the direct >> instances of each one and returning all the instances of the class and >> its subclasses. Is this correct? >> > > No. > > The notion is that reasoning is the job of the reasoner and that the > OntAPI provides convenient access to that, but doesn't duplicate it. There > are a few special cases but in general if you want reasoning then configure > a reasoner. > > > Now regarding listInstances(true), I am supposing that it should return >> all direct instances of the class, even if these instances are also >> instances of a subclass (which for example can happen if I load the >> TestInference.rdf file). >> > > No. That's the point of direct, as it says in the javadoc setting > direct=true means "excluding sub-classes of this class". > > If something is also an instance of a subclass of C then it is not a > direct instance of C and should not be returned by listInstances(true). > > Dave > > -- http://www.flickr.com/photos/papadako
